TAMR involves raising the temperature of a small region of the magnetic medium to near its Curie temperature where its coercivity and anisotropy are significantly reduced and magnetic writing becomes easier to achieve even with weak write fields characteristic of small write heads in high recording density schemes. In TAMR, optical power from a light source is converted into localized heating in a recording medium during a write process to temporarily reduce the field needed to switch the magnetizations of the medium grains. Thus, data storage density in a hard disk drive (HDD) in terms of kTPI (thousands of tracks per inch) can be further improved.
Optical power is delivered to the NFT by means of a dielectric waveguide where light from the waveguide is coupled into a NFT resonant mode, and specifically to a substantial portion of the NFT called the resonator body. Then, the NFT resonant mode is coupled to a small portion of the magnetic medium to generate a heating spot through a NFT peg feature, hereinafter referred to as the peg that has one end abutting the air bearing surface (ABS). The peg down-track and cross-track dimensions at the ABS largely dictate optical power intensity on the magnetic recording layer. Waveguide light typically originates from a diode mounted on the back side of a slider and has a wavelength of about 800 nm. The light may be in a transverse electric (TE) or transverse magnetic (TM) mode.
A critical requirement for proper TAMR operation is that the integrity of the peg must not be compromised since even a subtle peg shape change can cause a drastic drop in TAMR performance. Current state of the art TAMR NFTs usually comprise a so-called plasmonic material such as Au or an alloy thereof which has optical properties conducive to efficient excitation of the NFT resonance by waveguide light. Unfortunately, the most optically favorable materials for use in NFTs also have poor thermo-mechanical properties. This relationship presents a problem because the NFT is required to operate at elevated temperatures in an environment subjected to considerable mechanical stress. Furthermore, the peg is at the ABS and there is a possibility of a head disk interaction (HDI) event where the write head accidentally contacts a high point on the disk surface. Therefore, a new NFT structure is needed to provide peg shape integrity while maintaining acceptable optical transmission efficiency.